OPEN CALL – SOFTWARE DEFINED NETWORKING
Fig. 1. OpenCache Architecture
III. EVALUATION ON THE GÉANT OPENFLOW FACILITY (GOFF)
In order to evaluate the efficacy of OpenCache, we carried out a number of single and multiple client VoD streaming experiments representing different scenarios over the GOFF (one experimentation deployment is depicted in Fig. 2). During our experiments the video files are streamed using an adaptive video streaming technology, namely DASH (Dynamic Adaptive Streaming over HTTP) [5]. The main aim of our tests was to evaluate OpenCache's impact on the network link utilisation and its potential impact on the QoE of the endusers. To this effect, and influenced by related work [6-8], we defined four key QoE metrics, namely, (a) startup time, (b) bitrate changes during playback, (c) average bitrate achieved during playback (weighted based on its duration) and (d) minimum bitrate requested during playback. The results from our experimentation clearly demonstrate the benefits of OpenCache that provide two to six times quicker start up time (depending on the scenario) and significantly less bitrate oscillation during playback. In addition, the results show that OpenCache increases both the average weighted bitrate up to three times and the minimum bitrate up to six times, depending on the network link characteristics.
IV. CONCLUSION
As is being demonstrated through extensive experimentation on GOFF, OpenCache provides caching very close to the user with three important contributions. Firstly, the external link usage is reduced leading to lower transit traffic costs and improved network utilisation as end-user requests are now served locally. Secondly, OpenCache reduces the distribution load on the origin content provider and all the transient networks along the path between the origin and the end-user. Thirdly, by transparently caching the content closer to the end-user, OpenCache minimises the distance between the VoD streaming server and the user. This provides significant improvements to the Quality of Experience of the end-user. Our evaluation on GOFF demonstrates that the end-user’s streaming application observes higher minimum and average streaming bitrate, less bitrate oscillation and finally, quicker start up and buffering times; key QoE differentiators [6-8].
Fig. 2. Experimentation Deployment on the GÉANT OpenFlow Facility
ACKNOWLEDGMENT The work presented in this article has been funded by the EU FP7 GN3plus project (FP7-INFRASTRUCTURES-605243) and the EU FP7 OFELIA project (FP7-ICT-258365).
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For more information on GÉANT Open Call see www.geant.net/opencall 35